Effect of anticancer therapy on Tn antigen exposure on the leucocyte membranes in patients with leukemia

Abstract

Tn-antigen (Thomsen-nouvelle antigen) is tumor-associated carbohydrate antigen with only one GalNAc residue attached to serine or threonine of polypeptide chain. There is not enough data about the expression of this glycotope in hematologic processes. But the correlations between increasing Tn-antigen expression on the cell surface and tumor growth progression, invasion, and activation of cell migration are well known. Therefore, the currently important area of modern research is studying of the impact of anticancer therapy by expression of this carbohydrate antigen in the onco-proliferative process. There are two types of cytostatic therapies in clinical hospitals of Ukraine: COP-therapy (cyclophosphamide, vincristine, prednisone) and FC-therapy (fludarabine, cyclophosphamide), which are the most popular due to their effectiveness and low price. The aim of our study was to investigate Tn-antigen exposure on the surface of lymphocytes, monocytes and granulocytes in polycythemia vera and subleukemic myelosis; to examine the influence of COP- and FC-therapies on Tn-antigen exponation in patients with chronic lymphocytic leukemia. The objects of the study were blood cells of patients with chronic lymphocytic leukemia (n = 25), polycythemia vera (n = 15) and subleukemic myelosis (n = 15) aged 58–66 years. Healthy hematologic volunteers (n = 15) aged 55 to 65 years were in the control group. Lymphocytes of patients with chronic lymphocytic leukemia (n = 25) were also studied after the chemotherapy treatment of patients divided into two groups: those who took COP-therapy (n = 13); and those who treated with FC-therapy (n = 12). Tn-antigen exposure on lymphocytes, monocytes and granulocytes was investigated by Beckman Сoulter EPICS flow cytometer with primary monoclonal Tn-antigen anybodies (Institute of Immunology, Moscow, Russia) and secondary fluorescein isothiocyanate labeled antybodies (Millipore, USA). The number of dead cells was monitored by binding them with propidium iodide. The result was analyzed with FC Express. According to our data, Tn-antigen exposure was not detected on the surface of blood cells (lymphocytes, monocytes and granulocytes) in the control group and in patients with polycythemia vera and subleukemic myelosis. Nevertheless, Tn-antigen was identified on the surface of more than 80% of lymphocytes in chronic lymphocytic leukemia patients. The intensity of this tumor-associated antigen exposure on lymphocytes membrane was 100 times higher compared with that in normal lymphocytes. In chronic lymphocytic leukemia patients after COP-treatment the number of lymphocytes with surface Tn-antigen was equal to 28,1 ± 0,8%, and after FC-treatment it decreased to 9,5 ± 0,5%. Moreover, positive effect of cytotoxic therapy used in treatment of patients with chronic lymphocytic leukemia on intensity of Tn-antigen exposure on the surface of lymphocytes was shown. FC-therapy (fludarabine, cyclophosphamide) is more effective; compared with the data prior to this treatment it 40 times reduced the relevant index. Therefore, it can be applied in Ukraine for chemotherapeutic treatment schemes effective against Tn-antigen.